// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_URL_REQUEST_URL_REQUEST_CONTEXT_GETTER_H_
#define NET_URL_REQUEST_URL_REQUEST_CONTEXT_GETTER_H_

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/observer_list.h"
#include "base/sequenced_task_runner_helpers.h"
#include "net/base/net_export.h"

namespace base {
class SingleThreadTaskRunner;
} // namespace base

namespace net {
class CookieStore;
class URLRequestContext;
class URLRequestContextGetterObserver;

struct URLRequestContextGetterTraits;

// Interface for retrieving an URLRequestContext.
class NET_EXPORT URLRequestContextGetter
    : public base::RefCountedThreadSafe<URLRequestContextGetter,
          URLRequestContextGetterTraits> {
public:
    // Returns the URLRequestContextGetter's URLRequestContext. Must only be
    // called on the network task runner. Once NotifyContextShuttingDown() is
    // invoked, must always return nullptr. Does not transfer ownership of
    // the URLRequestContext.
    virtual URLRequestContext* GetURLRequestContext() = 0;

    // Returns a SingleThreadTaskRunner corresponding to the thread on
    // which the network IO happens (the thread on which the returned
    // URLRequestContext may be used).
    virtual scoped_refptr<base::SingleThreadTaskRunner>
    GetNetworkTaskRunner() const = 0;

    // Adds / removes an observer to watch for shutdown of |this|'s context. Must
    // only be called on network thread. May not be called once
    // GetURLRequestContext() starts returning nullptr.
    void AddObserver(URLRequestContextGetterObserver* observer);
    void RemoveObserver(URLRequestContextGetterObserver* observer);

protected:
    friend class base::RefCountedThreadSafe<URLRequestContextGetter,
        URLRequestContextGetterTraits>;
    friend class base::DeleteHelper<URLRequestContextGetter>;
    friend struct URLRequestContextGetterTraits;

    URLRequestContextGetter();
    virtual ~URLRequestContextGetter();

    // Called to indicate the URLRequestContext is about to be shutdown, so
    // observers need to abort any URLRequests they own.  The implementation of
    // this class is responsible for making sure this gets called.
    //
    // Must be called once and only once *before* context tear down begins, so any
    // pending requests can be torn down safely. Right before calling this method,
    // subclasses must ensure GetURLRequestContext returns nullptr, to protect
    // against reentrancy.
    void NotifyContextShuttingDown();

private:
    // OnDestruct is used to ensure deletion on the thread on which the request
    // IO happens.
    void OnDestruct() const;

    base::ObserverList<URLRequestContextGetterObserver> observer_list_;

    DISALLOW_COPY_AND_ASSIGN(URLRequestContextGetter);
};

struct URLRequestContextGetterTraits {
    static void Destruct(const URLRequestContextGetter* context_getter)
    {
        context_getter->OnDestruct();
    }
};

// For use in shimming a URLRequestContext into a URLRequestContextGetter.
class NET_EXPORT TrivialURLRequestContextGetter
    : public URLRequestContextGetter {
public:
    TrivialURLRequestContextGetter(
        URLRequestContext* context,
        const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner);

    // URLRequestContextGetter implementation:
    URLRequestContext* GetURLRequestContext() override;

    scoped_refptr<base::SingleThreadTaskRunner> GetNetworkTaskRunner()
        const override;

private:
    ~TrivialURLRequestContextGetter() override;

    URLRequestContext* context_;
    const scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;

    DISALLOW_COPY_AND_ASSIGN(TrivialURLRequestContextGetter);
};

} // namespace net

#endif // NET_URL_REQUEST_URL_REQUEST_CONTEXT_GETTER_H_
